An emergency alert was sent mistakenly to Hawaii's residents warning of an imminent ballistic missile attack when an employee at the state emergency management agency pushed the "wrong button," according to Hawaii's Governor.

Key points:

The alert that aired on television and radio was officially cancelled about 38 minutes after it was sent

Governor David Ige said it was sent during an employee shift change

Some residents became "hysterical, crying" and "lost it"

State officials and the United States military's Pacific Command confirmed there was no actual threat to the state.

The mistaken alert, which triggered panic among many Hawaiians who scrambled to find shelter, stated: "EMERGENCY ALERT BALLISTIC MISSILE THREAT INBOUND TO HAWAII. SEEK IMMEDIATE SHELTER. THIS IS NOT A DRILL."

The alert, sent to mobile phones and aired on television and radio, was officially cancelled about 38 minutes after it was sent.

Governor David Ige, who apologised for the mistake, said the alert was sent during an employee shift change at the Hawaii Emergency Management Agency.

"It was a procedure that occurs at the change of shift where they go through to make sure that the system, that it's working. And an employee pushed the wrong button," he said, adding that such shift changes occur three times a day every day of the year.

"I was awakened by the alert like everyone else here in the state of Hawaii. It was unfortunate and regrettable.

"We will be looking at how we can improve the procedures so it doesn't happen again."